You must take a corrective distribution of the excess annual additions and the taxable amount of that distribution is reportable on line 16b (not line 7) for the year distributed, not for the year the excess additions are made. There is no early withdrawal penalty on the taxable portion. What gets complex is the plan determination of how much comes from after tax contributions, pre tax deferrals and earnings, but the taxable amount will show in Box 2a. The distribution is paid to you and it is NOT rollover eligible.
Now if you already took a distribution, in service or otherwise and rolled it over to an IRA, since the excess amount is not eligible for rollover, you have an excess contribution to the IRA. This is treated as an excess regular contribution that is corrected in the usual manner if done before the extended due date. Earnings on the excess in the IRA are taxable are subject to penalty. If all this is not addressed before the extended due date (10/15 of the year following the year of the rollover or conversion), then you will owe a 6% excise tax for each year the excess remains in the IRA. There are automatic corrective actions that can reduce the excess and that is handled on Form 5329.
On top of the tax and penalties which can vary based on the type of IRA the rollover went to and when it is corrected relative to the extended due date, you will have a messy reporting situation since the IRS does not specify a reporting template. Since the excess was not rollover eligible, it would be reported as if it had not been rolled over on Form 1040 but since you will get a 1099R for both the plan distribution and the IRA corrective distribution, you have to explain to the IRS what happened so you will not be taxed twice on the same amount. If the excess distributed from the plan is after tax, you must get the 8606 correct if the amount goes to a TIRA before the Roth since this basis will not stay in your TIRA if it is removed as an excess IRA contribution. Or you might have rolled the excess directly from the plan to your Roth IRA which will not involve an 8606 so this is somewhat easier to handle and report.